Modern vehicles include one or more data buses that facilitate communication between electronic control units (ECUs) that monitor and control various vehicle subsystems. On-board diagnostics (OBD) facilitate the ECUs performing diagnostics and reporting the results via the data buses. Vehicles include connectors, such as OBD-II connectors, that allow external diagnostic tools to be coupled to the vehicle data buses to interact with the diagnostics of the ECUs. For example, a vehicle repair facility may connect to the OBD-II port to obtain information to determine why an engine check light is illuminated.